1. Field of the Invention
The present invention relates to a disk device, and, in particular, to a disk device which performs information recording and reproducing on any of a plurality of types of disks on which recording and reproducing are performed at different disk rotation speeds.
2. Description of the Related Art
In a conventional 3.5-inch FDD (Floppy Disk Drive), generally, the rotation speed of a disk is set to either 300 rpm or 360 rpm in accordance with the type of the disk. In a high-capacity FDD, because a negative-pressure-type magnetic head is used as a recording and reproducing head, it is necessary to rotate a disk at high speed (3600 rpm).
Therefore, when the high-capacity FDD has an arrangement such that the high-capacity FDD can perform recording and reproducing on a type of a disk on which recording and reproducing is performed by the conventional 3.5-inch FDD, it is necessary to contrive a disk-motor control method for this purpose.
The negative-pressure-type magnetic head will now be simply described.
The negative-pressure-type magnetic head used for performing recording and reproducing on a high-capacity floppy disk is disposed so that the disk (magnetic sheet) does not come into contact with the magnetic head when the disk cartridge is loaded in the disk device. Then, as a result of the disk being rotated at high speed, a negative pressure occurs between the magnetic-head surface and the disk surface, by which the magnetic sheet is attracted to the magnetic head, and recording and reproducing is performed on the disk by the magnetic head. That is, the negative-pressure-type magnetic head has a property reverse to a property of a floating-type magnetic head used in an HDD (Hard Disk Drive).
When a high-capacity floppy-disk cartridge is loaded in the disk device, as a result of the disk rotating at high speed, that is, 3600 rpm, the spindle motor is controlled so that the spindle motor stops rotating when the high-capacity floppy-disk cartridge is ejected from the disk device. However, due to the inertia of the spindle motor, when the high-capacity floppy-disk cartridge is ejected, a maximum time of approximately 2 sec. is required for the spindle motor to completely stop.
The shape of a high-capacity floppy-disk cartridge has an arrangement approximately the same as that of the low-capacity floppy-disk cartridge.
FIG. 1 shows a plan view of a floppy-disk cartridge, and FIG. 2 shows a sectional view in which a floppy disk is loaded on a spindle motor of a disk device.
In the floppy-disk cartridge 41, a hub 43 is fixed at the center of a disk-shaped recording medium 42. The recording medium 42 is covered by a resin shell 44. An opening 45 is formed in the shell 44. The opening 45 is usually covered by a shutter 46. The shutter 46 is opened so as to cause the opening 45 to be uncovered when the disk cartridge 41 is loaded in a predetermined position of a disk device. When the shutter 46 is open, a portion of the recording medium 42 is exposed from the shell 44 through the opening 45.
The hub 43 is exposed from the shell 44, and engages with a chucking stand 53 fixed to a rotation shaft 52 of a spindle motor 51. The hub 43 is made of metal, and is fastened onto the chucking stand 53 as a result of a magnet 50 fixed to the chucking stand 53 attracting the hub 43.
A positioning hole 47 is formed in the hub 43 of the recording medium 42. A driving pin 48 planted on the spindle motor 51 engages with the positioning hole 47.
A distinguishing hole 49 for distinguishing the type of the floppy disk is formed in the shell 44. When the floppy-disk cartridge 41 is loaded in the disk device, the position of the distinguishing hole 49 is detected by a plurality of microswitches, and, thereby, it is determined whether the loaded floppy disk is the high-capacity floppy disk or the low-capacity floppy disk.
FIGS. 3A, 3B and 3C show a process in which the positioning hole 47 of the floppy disk (recording medium 42) is engaged by the driving pin 48 of the spindle motor 51. FIG. 3A shows a condition immediately after the floppy disk (recording medium 42) is loaded on the chucking stand 53, FIG. 3B shows a condition in which the spindle motor 51 is rotated and the driving pin 48 is inserted into the positioning hole 47, and FIG. 3C shows a condition after the driving pin 48 engages with the positioning hole 47.
When the floppy-disk cartridge 41 is loaded in the predetermined position of the disk device, the driving pin 48 is not always inserted in the positioning hole 47, as shown in FIG. 3A. Then, the spindle motor 51 is slowly rotated, and, thereby, the driving pin 48 is caused to be inserted into the positioning hole 47, as shown in FIG. 3B.
As a result of further rotation of the spindle motor 51, the driving pin 48 comes into contact with the rotation-direction end of the positioning hole 47, as shown in FIG. 3C, and the rotation-driving force of the spindle motor 51 is positively transmitted to the hub 43.
In the disk device in the related art, when an ejecting button is pressed unsatisfactorily, and, then, the ejecting button is returned, the disk is once removed from the chucking stand of the spindle motor, and, then, the disk is again chucked onto the chucking stand.
When the low-capacity floppy-disk cartridge is loaded in the disk device, the spindle motor rotates at a relatively low speed. However, when the high-capacity floppy-disk cartridge is loaded in the disk device, the spindle motor rotates at a speed equal to or more than ten times the speed of the low-capacity floppy-disk cartridge. Therefore, the high-capacity floppy disk may be seriously damaged as a result of the above-mentioned situation, in which the disk is once removed from the chucking stand, and, then, the disk is again chucked onto the chucking stand, occurring while the spindle motor is rotating at the high speed.
Further, when the spindle motor starts running, the rotation speed of the spindle motor is sharply increased in the related art. Thereby, the spindle motor races without engagement of the driving pin of the chucking stand with the positioning hole of the hub of the floppy disk, and, thereby, the driving pin and/or the hub may be damaged.